ANTIOCH, Calif. — The twisted kidnapping case of a woman reportedly held captive for 18 years in a secluded backyard compound took another disturbing turn Friday as authorities searched the home of her alleged captor for evidence in the slayings of several prostitutes.

Several of the women's bodies — the exact number is not known — were dumped near an industrial park where Garrido, a sex offender, worked during the 1990s.

Garrido, 58, and his wife, Nancy, 54, were held without bond Friday after pleading not guilty to a total of 29 felony counts, including forcible abduction, rape, sexual assault and false imprisonment in connection with the abduction of 11-year-old Jaycee Lee Dugard in 1991. Authorities allege the Garridos held Dugard and two children she reportedly had with Garrido as prisoners in a backyard encampment.

Meanwhile, questions arose over how Garrido's alleged kidnapping crime went undetected for so long.

His neighbors knew he was a registered sex offender. Kids on his block called him "Creepy Phil" and kept their distance. Parole agents and local law enforcement regularly visited his home and found nothing unusual, even after a neighbor complained children were living in a complex of tents in his backyard.

For 18 years, Garrido managed to elude detection as he pulled off what authorities are calling an unfathomable crime, kidnapping Jaycee, keeping her as his secret sex slave for nearly two decades and fathering her two children.

Missed opportunitiesAuthorities acknowledged that they blew a chance in 2006 to rescue Dugard from the backyard labyrinth of sheds, tents and outbuildings that were concealed from the outside world.

A neighbor called 911 in November 2006 and described Garrido as a psychotic sex addict who was living with children and had people staying in tents in his backyard.

The investigating officer spent a half-hour interviewing Garrido on his front porch but did not enter the house or search the backyard, Contra Costa County Sheriff Warren E. Rupf said. The deputy, who did not know Garrido was a registered sex offender even though the sheriff's department had the information, warned Garrido that the tents could be a code violation before leaving.

"We missed an opportunity to bring earlier closure to this situation," Contra Costa County Sheriff Warren E. Rupf acknowledged. "I cannot change the course of events but we are beating ourselves up over this and continue to do so."

"We should have been more inquisitive, more curious and turned over a rock or two."

As a parolee, Garrido wore a GPS-linked ankle bracelet that tracked his every movement, met with his parole agent several times each month and was subject to routine surprise home visits and random drug and alcohol tests, California Department of Corrections and Rehabilitation spokesman Gordon Hinkle said.

Video: Hiding in plain sight (on this page)
The last unannounced visit by a team of local police agencies was conducted in July 2008. Paramedics also were summoned to the house five times since 1999, presumably to help Garrido's 88-year-old mother.

"There was never any indication to my knowledge that there was any sign of children living there," Hinkle said.

As it turns out, Dugard and her two children were living there as virtual prisoners, authorities say. The compound was arranged so that people could not view what was happening, and one of the buildings was sound-proofed and only accessible from the outside.

Neighbors knew there were children living there. Damon Robinson has lived next door to the Garridos for more than three years and his then-girlfriend in 2006 told him she saw tents in the backyard and children.

'Kept to himself'
Video: Stepfather: Girl's return is a 'miracle'
Dugard, now 29, was reunited with her family and said to be in good health, but feeling guilty about developing a bond with Garrido over the years. Her two children, 11 and 15, remained with her.

"Jaycee was really a mellow girl, so that’s probably what kept her alive. She just bonded with this guy and she didn’t try to get away and it probably kept her alive," her stepfather, Carl Probyn, told NBC's TODAY sahow on Friday. "If she would have been really spunky and fight and try to escape, maybe she would have been killed. It’s just a shock after 18 years that she’s still around."

Probyn has been in constant contact with Dugard's mother, his ex-wife Terry Probyn, since she found out her daughter was alive on Wednesday.

Probyn said both mother and daughter are trying to avoid the public eye for now. After not seeing each other for 18 years, Dugard greeted her mother by saying, "Hi, mom, I have babies," according to Probyn. Dugard had her two daughters with her at the reunion, and it appears she never told them she was kidnapped by their father, he said.

The authorities say they do not yet know whether she ever tried to alert anyone of her whereabouts, but she had chances to escape Garrido, who did a stint behind bars during the period of captivity.

"I tell you here's the story of what took place at this house, and you're going to be absolutely impressed. It's a disgusting thing that took place from the end to the beginning. But I turned my life completely around," he said.

He told the television station that he walked into the FBI's San Francisco office on Monday with Dugard's daughters and dropped off several documents containing rambling passages about religion, sexual compulsion and mind control.

FBI spokesman Joseph Schadler confirmed Garrido left the documents with the agency, but declined to discuss any further details.

Met wife while in prisonGarrido was required to register as a sex offender because he was convicted in 1977 of kidnapping a 25-year-old woman from parking lot in South Lake Tahoe, the same town Jaycee Dugard lived in when she was snatched from a school bus stop.

He was convicted of raping the woman multiple times at a Reno storage unit that the investigator from the case described as a "sex palace." It featured various sex aids, sex magazines and videos, stage lights, wine, and a bed, said investigator Dan DeMaranville.

Gail Powell, spokeswoman for the Nevada Department of Public Safety, said Garrido met his wife while he was serving time for the rape at the federal penitentiary in Leavenworth, Kan.

He served about 10 years of a 50-year federal sentence for kidnapping, and less than a year for a concurrent Nevada sentence of five years to life in prison for sexual assault. He was paroled in 1988, said Nevada Department of Corrections spokeswoman Suzanne Pardee.

A violation of Garrido's parole conditions sent him back to federal prison from April to August of 1993. Dick Carelli, spokesman for the federal Office of Court Administration, did not know what Garrido did to violate parole. Authorities are trying to piece together how and by whom Dugard was held during Garrido's four-month absence.

No ban on child contactHinkle said the alarm raised by the neighbor who contacted the sheriff's department in 2006 never was relayed to Garrido's parole agent. But there was no ban on him having contact with children, nor restrictions on his travels.

Hinkle said Garrido's parole agent was shocked Tuesday when University of California, Berkeley, police told him that the man he had been monitoring for years had been seen with two small children.

The agent, whom officials refused to name or make available for interviews, called Garrido into his office the next day. Garrido arrived with his wife, the children and a woman who initially identified herself as Allissa. She turned out to be Dugard and investigators said Garrido confessed to the kidnapping.

Monica Adams, 33, whose mother lives on their street, said she knew Phillip Garrido was a sex offender and that he had children living with him. Other neighbors knew, too, but they assumed police were keeping tabs on him.

Probyn said he was frustrated to find out that a car matching the description of the one he saw speeding Dugard away in the day she was kidnapped was found in the yard of Garrido's home. Nancy Garrido also fits the "dead-on" description he gave of the woman who pulled her into the car, he said.

"He had every break in the world," Probyn said of Garrido's close encounters with the law.

NBC News, The Associated Press and most other media, as a matter of policy, avoid identifying victims of alleged sexual abuse by name in its news reports. However, Dugard's disappearance had been known and reported for nearly two decades, making impossible any effort to shield her identity now.